JPH08296417A - Cylinder head for engine - Google Patents

Abstract

PURPOSE: To provide a cylinder head which has high freedom degree in a port design, has small heat resistance of a valve seat, and is firmly joined with the valve seat. CONSTITUTION: A cylinder head main body 11 is formed by Al-Si-Mg based aluminum alloy. A valve seat base metal 20 is formed by covering an iron based sintered alloy circular ring body 21 with a copper coat 22. The valve seat base metal 20 is pressed against combustion chamber side port opening parts 13a, 14a and joined therewith by heated with resistance heat generated by energization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine cylinder head in which valve seats for intake valves and exhaust valves are joined to a cylinder head body.

[0002]

2. Description of the Related Art Conventionally, a cylinder head body of an engine is mainly formed of an aluminum alloy, and a valve seat is attached to a portion of the cylinder head body where the valve face surface of an intake valve or an exhaust valve abuts. . This valve seat is formed of an iron-based sintered alloy or the like having excellent wear resistance and high-temperature strength because the intake / exhaust valve is repeatedly abutted and exposed to high heat, and as shown in FIG. It is integrally fixed to the cylinder head body by press-fitting into the recesses formed in the combustion chamber side openings of the intake port and exhaust port of the head and performing finish grinding.

FIG. 17 is an enlarged sectional view showing a valve seat press-fitting portion of a conventional cylinder head in which a valve seat is press-fitted. In FIG. 17, 1 is a cylinder head body, 2 is a press-fitting type valve seat, and 3 is a valve seat. The press-fitting recess is shown.

However, in the cylinder head in which the valve seat 2 made of a different material is press-fitted into the cylinder head body 1 as described above, the press-fitted valve seat 2 does not fall off even if the cylinder head becomes hot during operation. The press-fitting margin of the valve seat 2 must be taken to some extent. For this reason, the wall between adjacent ports needs to have a certain thickness or more, and the dimension between the ports cannot be reduced. That is, in the press-fitting type valve seat 2, the size of its cross-sectional area has been a major limitation in designing the area around the port of the cylinder head.

Further, the thermal conductivity of the iron-based sintered material as the material of the valve seat 2 is lower than that of the aluminum alloy as the material of the cylinder head body 1, and moreover, the valve seat 2
Has a certain thickness to prevent deformation during press fitting, and the valve seat 2 and the cylinder head body 1
Since there is a minute gap in the interface between the and, the thermal resistance when heat is transferred from the valve face of the intake / exhaust valve or exhaust to the cylinder head body 1 becomes large. Therefore, the cooling performance of the cylinder head may become insufficient, abnormal combustion may occur, and the temperature of the valve may rise excessively.

Further, the coefficient of thermal expansion of the material of the valve seat 2 is larger than that of the aluminum alloy which is the material of the cylinder head body 1, so that when the temperature reaches a certain level or more, a minute gap between the cylinder head body 1 and the valve seat 2 is generated. Spread, which further hinders the transfer of heat to the cylinder head body 1. As a result, the valve seat 2 itself is excessively heated, and the wear resistance and the like are likely to decrease.

In order to eliminate the above-mentioned problems caused by press-fitting the valve seat 2, a valve seat material having excellent heat resistance, wear resistance, and corrosion resistance is used as a heat source for the laser in the valve seat mounting portion of the cylinder head body 1. As a method, there is proposed a method of forming a valve seat by heating and melting, cladding (cladding), and machining the cladding layer (for example, see JP-A-62-150014). A valve seat formed by this laser clad method is shown in FIG.

FIG. 18 is an enlarged sectional view showing a valve seat portion of a cylinder head in which a valve seat is formed by a laser clad method. 4 is a valve seat portion, 5 is a bonding interface with the valve seat portion 4, and 6 is a joint interface. , 7 are molten reaction layers formed near the bonding interface 5.

Further, in a cylinder head for forming a valve seat by such a laser clad method, in order to increase the welding rate between the buildup layer and the cylinder head body, the welding surface of the cylinder head body is preliminarily plasticized by a rolling roll or the like. It has been proposed to perform the laser clad after forming the deformation layer (see, for example, Japanese Patent Application Laid-Open No. 2-196117).

[0010]

However, even if the valve seat is formed by the laser clad method as described above, there is a problem in the bonding strength because the valve seat material is melted and built up. This is because when the valve seat material is heated and melted, the portion of the cylinder head body 1 near the bonding interface 5 melts.

That is, since the part of the cylinder head body 1 is once melted and then solidified, a gas is generated and remains in the molten reaction layer 7 in the vicinity of the bonding interface as a blow hole, or a molten aluminum alloy. The molten reaction layer 7 is caused by solidification shrinkage when the solidification occurs.
Shrinkage cavities may occur inside. Further, this laser clad method has a problem in that it is easily affected by porosity and inclusions in the aluminum alloy material. In addition, the joint strength formed by melting and solidifying the material is apt to decrease the joint strength when the engine is operated for a long time under operating conditions such that the valve seat portion has a high temperature.

The present invention has been made in order to solve the above-mentioned problems, and the cross-sectional area and thermal resistance of the valve seat portion are reduced, and the engine is operated for a long time under operating conditions where the valve seat portion becomes hot. It is an object of the present invention to obtain a cylinder head in which the strength of the joint portion does not significantly decrease even when operating.

[0013]

A cylinder head for an engine according to the present invention is joined to a combustion chamber side port opening of a cylinder head body by pressing a valve seat base material and heating it with resistance heat generated by energization. The cylinder head body is formed of an Al-Si-Mg-based aluminum alloy, and the valve seat base material is formed of an iron-based sintered alloy annular body having a coating made of a metal material provided on the surface thereof. It is a thing.

[0014]

[Function] When the valve seat base material is brought into pressure contact with the port opening of the cylinder head body and heated, atoms at the interface of the pressure contact portion are mutually diffused, and the metal material of the film of the valve seat base material is near the interface. A layer made of a eutectic alloy with the material metal of the cylinder head body is produced. Since this eutectic alloy layer has a low transformation temperature to the liquid phase, it changes to the liquid phase under heating conditions, and the valve seat base metal is pressed and heated to cause plastic flow, which causes the material metal of the cylinder head body. Along with that, it is discharged from the joint.
As a result, the ferrous sintered alloy of the valve seat base material comes into contact with the material metal of the cylinder head body, causing the atoms of the two to diffuse into each other, and in this state the valve seat base material is buried in the port opening. become.

Further, the Al--Si--Mg type aluminum alloy used as the material of the cylinder head body has a smaller electric resistivity than other aluminum alloys used as the material of the cylinder head body for engines, and therefore has a smaller electric resistivity, so that it can be electrically conductive. Since the heat is generated efficiently and the resistance heat is easily transferred to the entire bonding interface due to the high thermal conductivity, it is difficult to form the molten layer due to the high solidus temperature, and the resistance value of 0.
Due to the small 2% proof stress, plastic flow is likely to occur.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
It will be described in detail by. FIG. 1 is a sectional view of a valve seat portion of a cylinder head according to the present invention, and FIG. 2 is a sectional view showing a state in which a valve seat base material is superposed on a port opening portion. Only a part is enlarged and drawn.

FIG. 3 is a front view of a pressing device used for joining the valve seat base material to the cylinder head body, FIG. 4 is a side view of the same, and FIG. 5 shows a state where electrodes are brought into contact with the valve seat base material. FIG. FIG. 6 is a graph showing a pressing force pattern, a current value pattern, and a sink amount, and FIG. 7 is a cross-sectional view showing a state in which an alloy layer made of the material metal of the film of the valve seat base material and the material metal of the cylinder head body is formed. FIG. 8 is a sectional view showing a state where the material metal of the cylinder head body is in plastic flow, FIG. 9 is a sectional view showing a state where the valve seat base material is buried in the cylinder head body, and FIG. 10 is a sectional view showing the valve seat portion. It is sectional drawing which shows the state which was finished. FIG. 11 is a plan view when a shield is used when energized.

FIG. 12 is a graph showing the relationship between the electrical resistivity of the aluminum alloy which is the material of the cylinder head body and the peeling load of the valve seat base material, and FIG. 13 is the thermal conductivity of the aluminum alloy which is the material of the cylinder head body. 5 is a graph showing the relationship between the peeling load of the valve seat base material and the peeling load. FIG. 14 is a graph showing the relationship between the solidus temperature of the aluminum alloy, which is the material of the cylinder head body, and the peeling load of the valve seat base material, and FIG. It is a graph which shows the relationship between 2% yield strength and the peeling load of a valve-seat base material.

In these figures, reference numeral 11 denotes a cylinder head body of a four-cycle engine. The cylinder head body 11 is formed by casting an aluminum alloy as a material, and has a dome-shaped recess 1 for forming a combustion chamber.
2 is formed so as to open on the lower surface, and an intake port 13 and an exhaust port 14 whose one end is open are formed in this recess 12.

As the aluminum alloy forming the cylinder head body 11, an Al-Si-Mg type aluminum alloy defined as JIS AC4C is adopted. The reason why this material is selected is that the valve seat described later can be joined most strongly as compared with the case of using other aluminum alloys.

Intake port 13 and exhaust port 14
Intake valve 1 through valve guides 15 and 16 on the upper wall
7 and exhaust valve 18 are installed respectively, and both ports 13,
Valve seats 19, which will be described later, are respectively joined to the openings of 14. The valve guides 15 and 16 have valve guide holes 11a formed in the cylinder head body 11.
It is press-fitted and fixed in. The valve guide hole 11a is formed so that its axis C coincides with the axes of the openings 13a and 14a of the intake port 13 and the exhaust port 14.

In the valve seat 19 shown in FIG. 1, a valve seat base material formed in an annular shape is used for the port opening portion 13.
a and 14a are joined by being brought into pressure contact with each other under a heating condition, and finished. The valve seat base material is indicated by reference numeral 20 in FIG. The valve seat base material 20 is formed by covering the surface of an iron-based sintered alloy annular body 21 with a copper film 22.

In the present embodiment, as the material of the annular body 21, a ferrous sintered alloy material in which copper is infiltrated is used from the viewpoint that resistance heat is less likely to be generated internally during energization, which will be described later. are doing. The copper film 22 has a film thickness of 0.1.
The annular member 21 is formed by electroplating so as to have a thickness of μm to 30 μm.

The valve seat base material 20, as shown in FIG. 2, has openings 13 of the intake port 13 and the exhaust port 14.
a part of the outer peripheral surface is overlapped with the opening 1
It is formed so as to face the insides of 3a and 14a. Note that FIG.
Then, the lower surface of the cylinder head body 11 (the surface where the combustion chamber forming recess 12 is opened) is directed upward. To elaborate,
The outer peripheral surface of the valve seat base material 20 is attached to the cylinder head body 1
The outer diameter of the valve seat base material 20 is gradually reduced toward the first side, and the bottom surface 20b is inclined.
Is gradually inclined toward the cylinder head body 11 side toward the axial center of the valve seat member 10, and the outer surface where the outer peripheral surface 20a and the bottom surface 20b are continuous is formed to be a convex curved surface. . In FIG. 2, this convex curved surface is denoted by reference numeral 20c. On the other hand, a convex portion 23 is formed in a portion of the opening 13a, 14a facing the convex curved surface 20c so that the inner diameters of the intake / exhaust ports 13, 14 are partially thin.

That is, by stacking the valve seat base material 20 on the openings 13a and 14a as shown in FIG. 2, the convex curved surface 20c is formed on the cylinder head body 1.
It is configured to come into contact with the first convex portion 23. In addition,
The inner peripheral surface of the valve seat base material 20 becomes closer to the cylinder head body 11 side as the valve seat base material 20 moves.
The inclined surface 20d is inclined so that the inner diameter of the inclined surface 20d is small, and the axially extending surface 20e extends from the inner peripheral side end of the inclined surface 20d in parallel with the axial direction.

The valve seat base material 20 thus constructed
The opening portions 13a, 14a of the cylinder head body 11
To bond to the press machine 24 shown in FIG. 3 and FIG.
Using. This press device 24 fixes a lower platen 26 to a lower portion of a base 25,
An upper platen 27 is disposed above and above the lower platen 26 so as to come in contact with and separate from the lower platen 26. The upper platen 27 is a rod 28 that serves as a working end of a cylinder device 28 that is attached to the upper part of the base so that the axis of the platen 27 is oriented vertically.
It is fixed to the lower end of a.

The lower platen 26 and the upper platen 27 have a structure in which power is supplied from a power supply device (not shown) via conductive members 26a, 27a, respectively. The conductive member 27a connected to the upper platen 27 is configured to be deformed or moved up and down according to the lifting operation of the upper platen 27. Further, in this embodiment, the upper platen 27 serves as an anode and the lower platen 26 serves as a cathode.

A reflecting member 29 fixed to the front part of the upper platen 27 is provided on the upper part of the base for supporting the cylinder device 28.
A laser displacement meter 30 that reflects the laser light and measures the amount of displacement of the upper platen 27 from the distance from the reflecting member 29 is attached to.

In order to bond the valve seat base material 20 using the press device 24, first, the lower platen 2 is joined.
The lower electrode 31 is fixed on the lower electrode 6, and the cylinder head body 11 is placed and fixed on the lower electrode 31. At this time,
The cylinder head body 11 has the combustion chamber forming recess 12 side facing upward, and the axis line at the opening of the port for joining the valve seat base material 20 has the rod 2 of the cylinder device 28.
Position it so that it coincides with the axis of 8a.

Next, as shown in FIG. 5, the guide rod 32 is fitted into the valve guide hole 11a of the port for joining the valve seat base material 20 from the combustion chamber forming recess 12 side. The guide rod 32 is formed by covering an outer peripheral surface of a metal round rod 32a with an insulating material 32b such as alumina. The guide rod 32 is fitted in the valve guide hole 11a and positioned and held by a stopper 32c. The length is formed so as to project upward from the end surface of the main body 11 on the combustion chamber side. In the present embodiment, the insulating material 32b is formed by spraying a ceramic material such as alumina on the round bar 32a and then polishing it.

Thereafter, the valve seat base material 20 is overlaid on the port opening, and the valve seat base material 20 is covered with the upper electrode 33.
Put. The upper electrode 33 has a through hole 33a formed in the axial center of a metal columnar body, into which the guide rod 32 is fitted, and the lower end thereof has the inclined surface 20d of the valve seat base material 20 (see FIG. 2) and a tapered peripheral surface 3b that is in close contact with the axially extending surface 20e over the entire circumference.
3c are formed. A magnetic body 33d for magnetically attracting the valve seat base material 20 is fixed to the lower end of the upper electrode 33.

That is, by fitting the guide rod 32 into the through hole 33a, the upper electrode 33 is positioned coaxially with the port opening portion of the cylinder head body 11, and the tapered surface 33b and the peripheral surface 33c are formed. By closely contacting the valve seat base material 20, the valve seat base material 20 is positioned by the fitting so as to be coaxial with the port opening.

After mounting the upper electrode 33 on the valve seat base material 20 in this manner, the upper electrode 33 is rotated to inspect whether the valve seat base material 20 is securely fitted.
Then, the cylinder device 28 is driven to drive the upper platen 2
7 is lowered and brought into close contact with the upper electrode 33. At this time, the lower surface of the upper platen 27 and the upper surface of the upper electrode 33 are made parallel to each other.

Next, the cylinder device 28 is driven to lower the upper platen 27, and the valve seat base material 20 is pressed against the cylinder head body 11 with a constant pressing force via the upper electrode 33. At this time, the direction of the pressing force applied to the valve seat base material 20 coincides with the axial direction of the port openings 13a and 14a because the movement direction of the upper electrode 33 is restricted by the guide rod 32. Therefore, the valve seat base material 20 has the port opening 1
It will be pressed along this axis with the axes aligned with 3a and 14a. This pressing force is changed based on the pressing force pattern shown by the solid line in FIG. That is, a relatively low constant first pressing force P1 is applied at the beginning of the joining process, and thereafter a relatively high constant second pressing force P2 is applied until the end of the descent.

After starting the pressurization by the first pressing force P1,
When the upper platen 27 becomes stable, the distance from the laser displacement meter 30 to the reflection member 29 is measured,
This distance is recorded as the lowering start position of the upper platen 27. Also, as shown in FIG. 6, after the time T1 has elapsed from the start of pressurization by the first pressing force P1, the upper platen 2
7 and the lower platen 26 are applied with a voltage, and a current is passed between the platens, that is, the upper electrode 33, the valve seat base material 20, the cylinder head body 11, and the lower electrode 31. At this time, the current flows from the upper electrode 33 toward the cylinder head body 11. The current value at this time is also changed based on the current value pattern shown by the broken line in FIG. That is, after the current value has increased, the current value is once reduced to around 0, and then the current value is further increased to zero the current value while the pressing force is being applied at the end of the joining.
And

At this time, in the valve seat base material 20, the convex curved surface 20c is in contact with the convex portion 23 of the cylinder head body 11 as shown in FIG. 2, and the area of the portion where these both come into contact is extremely small. Therefore, as described above, when electricity is applied, the electrical resistance increases and the contact portion generates heat. This heat is conducted to the entire contact interface between the valve seat base material 20 and the cylinder head body 11.

When the temperature of the contact interface between the valve seat base material 20 and the cylinder head body 11 rises in this way, the material metals (copper of the copper coating 22 and the aluminum alloy of the cylinder head body 11) that are pressed against each other in the solid state. ) Atoms become actively moving, and these atoms will diffuse into each other. It is not clear to what extent the aluminum oxide film formed on the surface of the cylinder head body 11 prevents this atomic diffusion from diffusing.

Due to the mutual diffusion of atoms as described above, the composition in the vicinity of the interface becomes a eutectic alloy of the copper constituting the copper coating 22 and the aluminum alloy of the cylinder head body 11, and has a temperature lower than that of pure copper. Then, it becomes possible to change from the solid phase to the liquid layer. The state near the interface at this time is schematically shown in FIG. In FIG. 7, a symbol A indicates a site where the mutual diffusion of atoms occurs and the eutectic alloy layer is generated.

When the temperature near the interface further rises and a part of the eutectic alloy layer changes to a liquid phase, the atom diffusion phenomenon becomes more active, and the eutectic alloy layer grows and grows. Along with this, the interface between the solid phase and the liquid phase expands. While the liquid phase of the eutectic alloy layer progresses, the aluminum alloy of the cylinder head body 11 adjacent to the eutectic alloy layer is heated by the resistance heat and the valve seat base material 20 being pressed. By doing so, plastic flow (plastic deformation) occurs.

Since this plastic flow occurs substantially symmetrically in the vertical direction in FIG. 7 around the first contact portion, the liquefied eutectic alloy is multiplied by the plastic flow as shown in FIG. Is excluded outside the contact area. In FIG. 8, the excluded portion of the eutectic alloy is indicated by the symbol B. At this time, a part of the copper film 22 of the valve seat base material 20 is eutectic alloyed and removed from the contact portion, so that a part of the torus 21 comes into contact with the aluminum alloy. Even during the period, the diffusion phenomenon of atoms occurs. A portion where this diffusion phenomenon occurs is indicated by a symbol C in FIG.

Since a part of the eutectic alloy layer is removed from the contact portion and the aluminum alloy causes plastic flow as described above, the valve seat base material 20 is cylinder-shaped when the valve seat base material 20 is indicated by T2 in FIG. It begins to sink into the head body 11. As described above, when the time T3 shown in FIG. 6 is reached after the valve seat base material 20 starts to sink, the pressing force is increased to the second pressing force P2.

As the pressing force increases, the amount of plastic flow of the aluminum alloy increases, and along with this, the amount of eutectic alloy to be excluded increases. As a result, a eutectic alloy made of a copper-aluminum alloy is newly generated in the unreacted portion of the contact portion, and the above-described phenomenon is repeated, and the eutectic alloy layer is liquid-phased and further eliminated. Along with this, the torus 21
The region where atoms mutually diffuse at the interface between the iron-based sintered alloy and the aluminum alloy, which are the materials, expands.

When the time T4 shown in FIG. 6 is reached after the pressing with the second pressing force P2 is started, the current value is once decreased to near 0 and further increased to the original value. By lowering the current value, heat generation is temporarily suppressed, the eutectic alloy is eliminated and plastic flow is suppressed, and as shown in FIG. 6, the rate of increase in the amount of depression of the valve seat base material 20 is temporarily reduced. . The reason for temporarily reducing the current value in this way is to prevent the aluminum alloy from being melted by heat.

After the current value is raised to the original value as described above, it is gradually reduced to 0 between the time T5 and the time T6. Not only while the current is flowing, but also after the power supply is cut off, the reaction proceeds until the temperature drops to the temperature at which the reaction cannot be performed, and the formation of the eutectic alloy layer → liquid layering → elimination associated with plastic flow , And the phenomenon of atomic mutual diffusion of the iron-based sintered alloy and the aluminum alloy simultaneously occur, the valve seat base material 20 continues to sink, and as shown in FIG. It will be buried in 11.

When the amount of subsidence does not substantially increase as shown in FIG. 6 (at time T7), the pressing by the cylinder device 28 is stopped and the distance between the laser displacement meter 30 and the reflecting member 29 is stopped. After determining the final position of the upper platen 27 from the above, the upper platen 27 is lifted and the cylinder head body 11 is removed from the press device 24. It should be noted that the average current value and the total energization time are also obtained by the time all steps are completed.

Next, the height difference from the lowering start position of the upper platen 27 to the final position is calculated to obtain the total sink amount of the valve seat base material 20. When this value is not within the range of the predetermined allowable value D (see FIG. 6), it is considered that the joining is defective. The allowable value D is about 0.
It was set to 5 mm to about 2 mm. The allowable value D varies depending on the material of the cylinder head body 11, but is approximately 1 mm to 1.5 mm.
It is preferable that

Cylinder heads that have passed the determination of the amount of sinking are judged as good or bad depending on whether or not the average current value or the total energization time is within the range of the allowable value, and this judgment result is judged to be good. The final finishing process is performed only when the lot has passed the sampling inspection described later.

The final finishing of the cylinder head is shown in FIG.
As shown in FIG. 10, the unnecessary portion is removed from the cylinder head main body 11 to which the valve seat base material 20 is joined, for example, by grinding, as shown in FIG. By performing this final finishing process, the unnecessary portion of the torus 21 and the copper coating 22 are removed, and the valve seat 19 joined to the cylinder head body 11 via the atom diffusion region indicated by the symbol C in FIG. can get.

The sampling inspection is carried out, for example, for each manufacturing lot of the valve seat base material 20, and the valve seat base material 20 in the state shown in FIG. This is done by applying a pulling force. More specifically, a jig is hooked on the inner peripheral edge of the bottom surface 20b (FIG. 2) of the valve seat base material 20, and a tension tester (not shown) is applied to the jig to apply tension along the direction. Then, when the load when the valve seat base material 20 is peeled from the cylinder head main body 11 exceeds the predetermined use limit peeling load, it is determined to be a good product.

Further, not only the peeling test of pulling the valve sheet base material 20 as described above but also the heat holding test or the heat shock test may be performed. In the heating and holding test, the cylinder head main body 11 in the state of FIG. 9 is left in a 300 ° C. heating furnace in the air atmosphere for 24 to 200 hours, air-cooled, and then the peeling test is performed. The heat shock test
The cylinder head body 11 in the state of FIG.
The temperature is raised to 300 ° C in a 00 ° C heating furnace, taken out of the furnace and immediately immersed in ice water at 0 ° C. This process is repeated 10 times, and every time when the valve sheet base material 20 is immersed in ice water and cooled, it is confirmed whether or not the valve sheet base material 20 is peeled or cracked, and finally the peel test is performed.

When performing the above-mentioned sampling inspection, it is visually determined whether or not the eutectic alloy removed from the joint extends over substantially the entire circumference of the joint. At this time, when it is determined that the removal direction of the eutectic alloy tends to be biased in a specific direction, the shield 34 is disposed near the upper electrode 33 as shown in FIG. It is preferable not to receive the part.

FIG. 11 is a plan view of the case where a shield is used, which shows a state in which the upper electrode 33 is attached to the cylinder head body 11 together with the valve seat base material 20. In the figure, the same or equivalent members as those described in FIGS. 1 to 10 are designated by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, the shield 34 is formed of an iron-based ferromagnetic material into a vertically split cylindrical shape, and is arranged so that the top of the outer peripheral surface faces the base 25 of the pressing device 24. The direction in which the base 25 is located is indicated by an arrow in the figure. By using the shield 34 in this way, it is possible to control the direction and amount of magnetic field lines when a magnetic field is generated during energization, and as a result, to control the direction in which the eutectic alloy is excluded from the joint. You can

In creating the present invention, the inventor changes the type of aluminum alloy as the material of the cylinder head body 11 and joins the valve seat base material 20 and conducts a peeling test for each type. The inventors have found an aluminum alloy that provides a peeling load that can be used as an engine valve seat. The results of this peel test are shown in FIGS.

In FIGS. 12 to 15, ◯ and ● are AC4C materials used in this embodiment, and ◇ and ♦ are AC4B.
The materials, □, and ■ are AC2B materials, all of which are specified by JIS, and are most often adopted as the material for the cylinder head body of the engine. The AC4B material is an Al-Si-Cu based aluminum alloy, and the AC2B material is an Al-Cu-Si based aluminum alloy.

The symbols ○, ◇, and □ all indicate the results of the peeling test with the valve seat base material 20 still bonded to the cylinder head body 11, and the symbols ●, and
The symbols ◆ and ■ show the results when the peeling test was carried out after the cylinder head body 11 to which the valve sheet base material 20 was bonded was left to stand in a 300 ° C. heating furnace in the air atmosphere for 24 hours and air-cooled. Peeling load is 2 after performing these peeling tests.
If it was 0 KN or more, the aluminum alloy material was considered to be acceptable.

As shown in FIG. 12, the electric resistivity is 7 to
The AC4C material in the range of 7.5 × 10 ⁻² μΩ · m, which is relatively smaller than the other aluminum alloy materials, passed both of the two types of peeling tests. It is considered that this is because it generates heat more efficiently when energized than other materials. As shown in FIG. 13, the thermal conductivity is 150 to 160.
The AC4C material, which is in the range of W / m · ° C and is relatively larger than the other aluminum alloy materials, passed both of the two types of peeling tests. It is considered that this is because resistance heat is more likely to be transmitted to the entire bonding interface than other materials.

As shown in FIG. 14, the solidus temperature is 55
The AC4C material, which is in the range of 0 to 560 ° C. and is relatively higher than other aluminum alloy materials, passed both of the two types of peeling tests. The solidus temperature is a temperature at which an aluminum alloy changes from a solid phase state to a liquid phase state, in other words, a temperature at which the aluminum alloy melts. It is considered that the reason why the AC4C material having a relatively high solidus temperature passed was that the molten layer was hard to be formed as compared with other materials.

As shown in FIG. 15, the 0.2% proof stress at 400 ° C. is in the range of 30 to 35 MPa, and AC4
The AC4C material, which is relatively smaller than the B material, passed both of the two types of peeling tests. At 400 ° C.
The 2% proof stress is a stress at which a plastic strain of 0.2% remains when a tensile test is performed on an aluminum alloy material at 400 ° C. AC4, which has a relatively small yield strength
It is considered that the reason why the material C passed was that plastic flow was more likely to occur than the material AC4B.

The metallurgical bond between the aluminum alloy of the cylinder head body 11 and the iron-based sintered alloy of the valve seat 19 in the cylinder head formed as described above is discontinuous as a material without atom diffusion. It is essentially different from the mechanical joining that is in the normal state. Moreover, it is also different from metallurgical joining such as resistance heat welding in which both materials are locally melted into an alloy solution by utilizing the heat generated by the electric resistance at the interface and then cooled and solidified by stopping the energization. Is.

That is, the metallurgical joining in the cylinder head of the present embodiment is performed without leaving a molten reaction layer between different materials, and is continuous through mutual diffusion of atoms at the interface between both materials. Is to create a unique structure.

In this embodiment, the valve seat base material 20 is used.
And port openings 13a, 14 of the cylinder head body 11
Although an example is shown in which convex portions (convex curved surface 20c, convex portion 23) are formed on both of a and the convex portions are pressed against each other, the convex portion does not necessarily have to be formed on both of them, and either It may be formed on only one side. This embodiment is shown in FIG.
It is shown in (c).

FIG. 16 is a sectional view showing another embodiment in which the shape of the pressure contact portion is changed. FIGS. 16A and 16B show an example in which a convex portion is formed only on the valve seat base material. (C) shows an example in which the convex portion is formed only on the cylinder head body.
In these figures, the same or equivalent members as those described with reference to FIGS. 1 to 10 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the example shown in FIG. 16 (a), the valve seat base material 20 is formed in the same shape as that of the above-mentioned embodiment, and the portions of the port openings 13a and 14a with which the valve seat base material 20 contacts are flat. It is an inclined surface. In the example shown in FIG. 2B, the outer peripheral surface of the valve seat base material 20 is configured to fit into the port openings 13a and 14a.
Further, the inner peripheral surface of the valve seat base material 20 is different from the above-mentioned embodiment, and the axially extending surface 20e is formed over the entire thickness direction of the valve seat base material 20. The same figure (c)
In the example shown in (1), the portion of the valve seat base material 20 that contacts the convex portion 23 of the cylinder head body 11 is a flat inclined surface. As shown in FIGS. 16 (a) to 16 (c), the convex portion is formed on the valve seat base material 20 and the cylinder head body 1.
Even if it is formed in any one of 1, the same effect as in the above embodiment can be obtained. When the convex portions are formed on both of the above as shown in this embodiment, the material metal of the cylinder head body 11 is likely to cause plastic flow, and the amount thereof is relatively large. The area of the portion (contact interface) where 20 is joined can be expanded, and high joining strength can be obtained.

Further, in the above-described embodiment, as the material of the annular body 21 of the valve seat base material 20, a ferrous sintered alloy in which copper is infiltrated is used, and the coating of the annular body 21 is copper. Although the example of providing by electroplating is shown, the material and the method of forming the film are not limited to this embodiment. That is, any material may be used as the material of the annular body 21 as long as it is an iron-based sintered alloy, and the metal infiltrated therein may be one having an electric conductivity which is not significantly different from that of copper. In addition, the metal forming the film of the torus 21 is also separated from the cylinder head body 11
Any material may be used as long as it can form a eutectic alloy with the material metal. In selecting the material and the method for forming the film, in this embodiment, the cost was the lowest because of the production of the cylinder head as an industrial product.

Furthermore, in the embodiment shown in FIGS. 1 to 10, an example in which the amount of depression of the valve seat base material 20 is detected at the end of the joining process is shown, but this amount of depression is always measured from the start of pressing, It may be possible to detect whether this value is within the allowable range at that time. By doing so, it is possible to determine that a defective joint has occurred during the joint process, so that it is possible to eliminate the waste of spending a joint time equivalent to that of a non-defective product even on a defective product.

[0066]

As described above, in the engine cylinder head according to the present invention, the valve seat base material is brought into pressure contact with the combustion chamber side port opening of the cylinder head body and is heated by resistance heat generated by energization. The cylinder head body is made of Al-Si-Mg.
Since the valve seat base material is formed of an iron-based sintered alloy annular body having a coating made of a metal material on its surface, the valve seat base material is formed in the port opening of the cylinder head body. By pressing and heating, atoms at the interface of the pressure contact part diffuse with each other, and a layer made of a eutectic alloy of the material metal of the film of the valve seat base material and the material metal of the cylinder head body is formed near the interface. Is generated. Since this eutectic alloy layer has a low transformation temperature to the liquid phase, it changes to the liquid phase under heating conditions, and the valve seat base metal is pressed and heated to cause plastic flow, which causes the material metal of the cylinder head body. Along with that, it is discharged from the joint.

As a result, the ferrous sintered alloy of the valve seat base material comes into contact with the material metal of the cylinder head body so that the atoms of the two materials diffuse into each other. In this state, the valve seat base material enters the port opening. It will be buried. Therefore, the valve seat can be joined by the mutual diffusion phenomenon of atoms instead of being press-fitted into the cylinder head body, and the mutual diffusion phenomenon occurs substantially uniformly over the entire circumference of the valve seat due to the pressing direction at the time of joining, which is high. It can be bonded with a bonding strength.

Therefore, there is no need to provide a press-fitting margin as compared with the case where the valve seat is press-fitted into the cylinder head main body, so that the sectional area of the valve seat portion can be reduced. As a result, the degree of freedom in design around the port of the cylinder head is increased. Along with this, the heat transfer resistance when heat is transferred through the valve seat is also small, so that the engine may cause abnormal combustion, or the valve seat may be worn or damaged due to thermal deterioration. It can be prevented.

Further, since a molten layer is not formed between the cylinder head body and the valve seat, defects in the vicinity of the joining interface between the two are extremely small as compared with the case where the valve seat is formed by the conventional laser clad method. Therefore, the valve seat can be bonded to the cylinder head body with high bonding strength. Moreover, even if the engine is operated for a long time under operating conditions where the valve seat becomes hot,
The strength of the joint does not significantly decrease.

In addition, the Al--Si--Mg-based aluminum alloy used as the material of the cylinder head body in the present invention has a higher thermal conductivity and a higher solidity than other aluminum alloys used as the material of the cylinder head body for engines. Phase line temperature is relatively high and electrical resistivity and 4
Since the 0.2% proof stress at 00 ° C is relatively small, the valve seat base material can be firmly bonded to the cylinder head body. In addition, since the Al-Si-Mg-based aluminum alloy is widely used and is not a special material, the cylinder head according to the present invention can be manufactured very easily.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a valve seat portion of a cylinder head in which valve seats are joined by a joining method according to the present invention.

FIG. 2 is a cross-sectional view showing a state in which a valve seat base material is overlapped with a port opening portion, and in the figure, only a part of the cylinder head main body and the valve seat base material is enlarged and drawn.

FIG. 3 is a front view of a pressing device used for carrying out the method for joining valve seats according to the present invention.

FIG. 4 is a side view of a pressing device used for carrying out the method for joining valve seats according to the present invention.

FIG. 5 is a cross-sectional view showing a state where an electrode is brought into contact with a valve seat base material.

FIG. 6 is a graph showing a pressing force pattern, a current value pattern, and a sink amount.

FIG. 7 is a cross-sectional view showing a state in which an alloy layer including a material metal of a film of a valve seat base material and a material metal of a cylinder head body is formed.

FIG. 8 is a cross-sectional view showing a state where the material metal of the cylinder head body is in plastic flow.

FIG. 9 is a cross-sectional view showing a state in which a valve seat base material is buried in a cylinder head body.

FIG. 10 is a cross-sectional view showing a state where the valve seat portion is finished.

FIG. 11 is a plan view when a shield is used.

FIG. 12 is a graph showing the relationship between the electrical resistivity of the aluminum alloy that is the material of the cylinder head body and the peeling load of the valve seat base material.

FIG. 13 is a graph showing the relationship between the thermal conductivity of the aluminum alloy that is the material of the cylinder head body and the peeling load of the valve seat base material.

FIG. 14 is a graph showing the relationship between the solidus temperature of the aluminum alloy that is the material of the cylinder head body and the peeling load of the valve seat base material.

FIG. 15 is a graph showing a relationship between a 0.2% proof stress at 400 ° C. of an aluminum alloy as a material of a cylinder head body and a peeling load of a valve seat base material.

FIG. 16 is a cross-sectional view showing another embodiment in which the shape of the pressure contact portion is changed, and FIGS. 16 (a) and 16 (b) show an example in which a convex portion is formed only on the valve seat base material, and FIG. ) Indicates an example in which the convex portion is formed only on the cylinder head main body.

FIG. 17 is an enlarged sectional view showing a valve seat press-fitting portion of a conventional cylinder head into which a valve seat is press-fitted.

FIG. 18 is an enlarged sectional view showing a valve seat portion of a cylinder head in which a valve seat is formed by a laser clad method.

[Explanation of symbols]

11 ... Cylinder head body, 13 ... Intake port, 13a
... Opening part, 14 ... Exhaust port, 14a ... Opening part, 17 ...
Intake valve, 18 ... Exhaust valve, 19 ... Valve seat, 20 ... Valve seat base material, 21 ... Torus, 22 ... Copper film, 31 ...
Lower electrode, 33 ... Upper electrode.

Claims (1)

[Claims] 1. In an engine cylinder head in which a cylinder head main body and a valve seat are made of different materials, a resistance generated by energizing a valve seat base material with a valve seat base material in pressure contact with a combustion chamber side port opening of the cylinder head main body. An iron-based sintered alloy that is joined by heating with heat, the cylinder head body is formed of an Al-Si-Mg-based aluminum alloy, and the valve seat base material is provided with a coating made of a metal material on the surface. A cylinder head for an engine, which is formed of an annular body.